1. Field of the invention
This invention pertains to connectors for optical fibers for use in the telecommunications and data transmission industries. More particularly, this invention pertains to a fiber optic connector having means to prevent an air gap in an adhesive retaining the fiber within the connector.
2. Description of the Prior Art
In the prior art, connectors for optical fibers are well known. Such connectors include a ferrule (which is typically ceramic) having an axially extending bore. The fiber is placed within the bore. Also, as is typical, the ferrule is retained within a ferrule holder (commonly referred to as a hub). To retain the fiber within the ferrule, an adhesive (commonly, epoxy) is admitted into the ferrule holder and forced under pressure into the bore of the ferrule. The fiber is passed through both the holder and the bore and is retained within the ferrule by means of the adhesive.
From time to time, air pockets may form within the adhesive which is urged into the ferrule holder. If air pockets are formed after the fiber is placed within the ferrule, the adhesive will harden resulting in an air pocket surrounding at least a portion of the fiber. Accordingly, that portion of the fiber is not supported by adhesive.
The presence of an unsupported segment of fiber within a connector is undesirable. The unsupported fiber can have stress points. Further, minute bends can occur in the fiber in the unsupported region due to unequal thermal expansion and contraction. Also, the unsupported fiber can possibly bend during vibration or shock which also increases the stress on the fiber. For these, and other reasons, the unsupported fiber is more susceptible to breakage.
In practice, the occurrence of undesirable air pockets and resulting breakage of fibers within a fiber optic connector is fairly rare. However, even small possibilities of breakage are undesirable. Optical fibers in use today carry signals at rates in excess of 2.4 gigabits per second. In terms of voice communications, a single fiber may be carrying in excess of thirty-two thousand simultaneous voice telephone conversations. As a result, the breakage of a single fiber can disrupt service to many telephone customers. The problems associated with such breakage is particularly acute with respect to data transmission since data can be lost in the event of a fiber breakage.
U.S. Pat. No. 5,206,921 which issued on Apr. 27, 1993 to Okada et al. teaches a ferrule (element F in the patent) secured within a support block 1 and sealed thereto by means of an O-ring 3. An axial end F3 of the ferrule is in communication with a passage 4 formed in the support block 1. By means of a suction unit 5, a suction is applied to the passage 4. An adhesive is placed in an aperture F1 while the suction is applied to passage 4. In reviewing U.S. Pat. No. 5,206,921, it is noted that the patent does not address the formation of air pockets or the resolution of the problem associated with air pockets. Instead, the patent is directed to the automated application of adhesive to the axial end F3 of the ferrule. The patent recognizes that due to prior manual adhesive attachment operations, the amount of time to place a mass of adhesive to the end of the ferrule was long and adhesives can, from time to time, adhere to the operator's hands or undesired areas of the ferrule.
It is an object of the present invention to provide means for preventing air pocket formation in a ferrule regardless of whether adhesive is applied manually or automated.